Manufacture of thioethers of alphaanthraquinone



Patented l, 1938 UNITED STATES PATENT- OFFICE MANUFACTURE OF THIOETHERS F ALPHA- ANTHRAQUINONE Troy Lee Cantrell and James btho Turner, Lansdowne, Pa., assignors to Gulf Oil Corporation, Pittsburgh, Pa., a corporation of Pennsylvania No Drawing. Application September 2, 1936,

Serial No. 99,160

Claims.

This invention relates to the manufacture of thioethers of alpha-anthraquinone and it comvprises methods of making such thioethers wherein an alkali metal salt of alpha-anthraquinone 5 sulfonic acid is reacted with an alkali metal merca'ptide, in an aqueous medium, the thioether so formed being isolated and recovered from the aqueous reaction mixture; and it also comprises the-thioethers of alpha-anthraquinone so prol0 duced, particularly the alkyl thioethers of alphaanthraquinone, these thioethers being useful as improvement agents for mineral lubricating oils and for other purposes; all as more fully hereinafter set forth and as claimed.

l5 We have found that various organic thioethers are excellent improvement agents for mineral lubricating oils. Most of these thioethers are miscible with hydrocarbons and these, when incorporated with mineral lubricating oils, improve go the lubricating. qualities thereof. Thioethers of alpha-anthraquinone, particularly the alkyl thioethers thereof, are excellent improvement agents for this purpose. When small amounts are incorporated in mineral lubricating oils, the nor- 25 mal destructive action of mineral lubricating oil deterioration products on certain alloy bearing surfaces is mitigated or retarded. Also, the film strength of the lubricant is markedly improved.

In our co-pending application Ser. No. 99,156, such so methods of improving mineral lubricating oils and the improved lubricant so obtained with the aid of these thioethers are described and claimed.

' The present application is directed to the thioether itself and methods of making the same. The thioethers made according to the present invention are particularly suitable for preparing the improved lubricants of our companion application.

The thioethers made according to the present invention may-be represented by the following formula:-

o'wherein R" represents a hydrocarbon radical,

advantageously an alkyl radical. As a class, these thioethers are soluble and miscible with mineral oils only in limited proportions. However, they are sufilciently soluble and miscible to permit incorporation with mineral oils of amount of thioether sufllcient to obtain the desired improvements.

Inthe present invention these thioethers are prepared from anthraquinone alpha sulfonic acid, that acid being first converted into a suit 5 able salt for the reactions here employed. Alkali metal sulfonates of alpha anthraquinone are advantageous and the sodium salt of this sulfonic acid, being 'easily prepared, is ordinarily employed. Such salts of anthraquinone alpha sull0 fonic acid are reactedjwith metal mercaptides in aqueous solution to introduce a thioether group into the alpha position. 'lhus we may prepare various thioethers ofalpha-anthraquinone by employing an appropriate mercaptan',

the mercaptan being first converted into a suitable metal mercaptlde. Again the alkali metal derivatives are advantageous, particularly the alkali metal alli'yl sulfides. The sodium mercaptides being easily prepared and quite effective in these condensations, are ordinarily employed. The reaction between the sodium salt of anthraquinone alpha sulfonic acid and sodium alkyl sulfide being typical, the following equation representing that reaction is illustrative of the condensation by which we obtain these thioethers of alpha anthraquinonez O OiNa By employing other sodium hydrocarbon sulfldes, various thioethers, may be obtained in a similar manner. Thus the R in the structural formula given ante may represent various hydrocarbon radicals, such as acyclic, cyclic or 0 heterocyclic, as well as simple aliphatic and arovan seous and are empl yed in the paration is +NMSO:

of most of our desired thioethers. With them the by=product sodium sulfite may be readily removed and separated from the thioether, for instance, by washing the thioether with water as more fully described post.

One advantageous starting material is the ethyl mercaptan; either the chemically pure or mercial aim'l mercaptans having the following properties are advantageous in producing thioethers of anthraquinone useful as improvement may contain a small amount of mercaptan."

alpha anthraquinone may be used it is advanagents for mineral oils:

In the above table the properties of ethyl 'mercaptan'are given for purposes of comparisonwith the properties of commercial amylmercaptan.

Any of these organic mercaptans may be readily converted into alkali metal mercaptides for the present purposes.- The thioether being formed from the me'rcaptide in an aqueous medium, the alkyl mercaptan is added to an aqueous caustic soda solution and the mixture is heated, if necessary, until the mercaptide is obtained. The solution of alkali metal mercaptide so prepared While we ordinarily employ the described procedure, the sodium 'alkyl mercaptide, when available as such, may be directly dissolved in water.

While any of the alkali metal sulfonates of tageous to employ the sodium salt. The sodium salt is readily soluble in'water and ordinarily we separately prepare an aqueous solution of the .alkali metal sulfonate and then admix this solution with. the solution of the mercaptide.

Informing the thioether we find it is advantageous to employ a slight excess of the mercaptide or mercaptan over that theoretically necessary to react with the alkali metal sulfonate. In this way substantially all ofthe anthraq'uinone compound is converted into the thioether, the presence of the mercaptide in slight excess causing a substantially complete precipitation of the thioether. Thus a high yield of anthraquinone thioether is obtained from the initial anthraquinone compound. However, during the mixing of the two solutions and during the early part of the reaction, we have found it advantageous to have the alkali metal sulfonate present in excess as the reaction is more easily controlled and a uniform reaction more readily obtained under such conditions. To obtain the desired conditions at each stage, we first heat the solution of the alkali metal sulfonate to about boiling temperature and then slowly add the alkali mercaptide solution; it being added at such a rate that no substantial excess of mercaptide is present until after the main reaction is subslight excess of mercaptide over that necessary to form the thioether. This mixture is then fur ther boiled under reflux to complete the reaction; this additional heating being continued until substantially all the thioether has been precipitated, ordinarily five to ten hours of heating being suiiicient to complete thereaction. At the end of the reaction the refluxing is discontinued and any mercaptan present is distilled oil and recovered. Sometimes it is advantageous to add a small amount of free mercaptan before the final heating to complete the reaction, the mercaptan beihg added for instance in the proportion of one to two percent by weight.

The thioether is then separated and recovered. It may be separated from the aqueous liquid by- .decantation, filtration or other suitable method,

depending upon. whether the particular thioether is a liquid or solid material. The separated thioethers may be further purified if desired. Being insoluble in water, they may be washed with water and thendried. The solid thioethers may be drained and dried in a current of warm air.

The wet liquid thioethers may be warmed and a current of air blown through the heated liquid to remove the residual moisture.

.In this way, thioethers, either liquid or solid at. room temperature and having a wide range of properties, may be obtained according to this invention.

As stated ante, alphaanthraquinone thioethers containing alkyl groups, such as' the various amyl groups, may be readily obtained by the method of the present invention. All the amyl compounds have advantageous properties. Of these the normal-amylthioether of alpha anthraquinone is typical; this amyl compound has the following formu1a:-

i I, I i s-m1. I

The thioethers obtained from the commercial -amyl mercaptans often contain all the possible isomers and, being mixed thioethers, are advantageous for certain purposes such as improving the qualities of mineral oils. There are some specific advantages in both normal-amyl and isoamyl compositions. The same is true-of thioethers derived from butyls and propyls; each having specific advantages in certain relationships.

Other alkyl thioethers which may be obtained by the present method are as follows:-

Alpha-anthraquinone-ethyl-thioether Alpha-anthraquinone-butyl-thioether Alpha-anthraquinone-propyl-thioether These specific thioethers, especially advanta geous for improvingpetroleum oils and mineral oil lubricants, as a sub-class may be represented by the following formulaz narily employed in the follows:;--

- Alkyl-thioeth'eroi Melting Percent Sulfur alpha-nnthrequinone point 0. thcoret. empiric. Color 180-185 11.62 11.40 Orange a 147-150 11. 40 ll. 27 Orange 108-110 10.82 10. 40 Goldenyellow Commercial amyl (mix- Oilatnor- 10.33 Goldenturefiin-amyland 130- me] temp. -yellow amy pha anthraquino'ne may be prepared as stated ante.

These thioethers are quite stable even at the elevated operating temperatures often encountered in the lubrication of alloy bearings. Also, they are substantially neutral in reaction. The properties of some of the alkyl thioethers, ordipresent invention, are as The above compounds are-insoluble in water,

, slightly ,soluble'in ethyl alcohol, and soluble in benzene. When crystallized as pure compositions from benzene they yield golden-yellow to red colored crystals.

The alnyl thioether, being liquid, has excellent blending qualities and is readily soluble in mineral oils at the usual blending temperatures, for instance from 120 to 280 F. .33 employing diflerent thioethers of alpha anthraquinone containing as the ether group any radical from either the aliphatic or aromatic series of hydrocarbons we can obtain products of various propfiltered to remove any solid or indissolved maerties, this being advantageous for particular embodiments of the present invention. These various products may be produced by selecting the proper mercaptan as the starting material.

Example 1.--An aqueous solution of sodium ansulfonate is prepared by dis-.

thraquinone alpha solving 320 pounds 5000 pounds of hot ing water.

of said sodium sulfonate in water, advantageously boil- If necessary the solution may be terial. Ordinarily this filtration is not neces-' saw as the usual commercial grades of this sodium salt are comparatively pure and no solid nor undissolved matter remains suspended in soluthe aqueous mercaptide solution is gradually added while continuing the boiling; about one hour being required to so mix the amounts of the two aqueous solutions given-ante. During this time the mixture is heated under reflux. After all the mercaptide solution is added, the mixture is further'boiled'under reflux for a period of five hours or more untilthe reaction is complete and substantially all the alpha anthraquinone ethyl thioethe'r has been tated.

.The mixture is then cooled and permitted to stand for about ten hours to permit complete settling of the precipitated thioether; the thioether settling to the bottomof the reaction vessel as a solid material. After thorough settling, the aqueous sodium sulfite liquor is removed by -The thioethers so obtained precipidecantation. The crystalline mass of thioether so obtained is then washed with two volumes of water to ,freegit from residual sodium suliite. The washed crystals are then air dried. The alpha anthraquinone ethyl thloether dry crystals have the following properties:'

Melting point r 1'ee- -'1es Sulfur per cent 11.40 Color -Orange This thioether may be represented by the following formulas-'- By employing a solution of sodium propyl i mercaptide or of sodium butyl mercaptide', in lieu of the ethyl compound in the procedure of Example 1, there is obtained the corresponding butyl or propyl thioether of alpha anthraqi'iinone.

structural formulae:-

have the following Anthraq ne al he with Ant 1 ulnone mbutyl v thieetber 0 The above alpha have the following properties:-

Al liaanthmquin- 3110 thioether Inspection Prop'yl Butyl Melting point F- 147-150 Suliur, percent. 11 27 Color 118-110 Orange 10- Golden- Example 2.-An aqueous. solution of sodium anthraquinone alpha sulfonate is prepared by dissolving 320 pounds of said sodium sulfonate in 5000 pounds of hot water, advantageously boillng water. If necessary the solution may be filtered to remoye any solid or undissolved material. Ordinarily this filtration is not necessary as the usual commercial grades of this sodium salt are comparatively pure and no solid nor undissolved n atter remains suspender in solution.

Separately there is prepared-an aqueous solution of sodium amyl mercaptide by adding 106 pounds of commercial amyl mercaptan to 800 pounds or 5.0% aqueous caustic soda solution,

the mixture being stirred and maintained at room temperature until the reaction is substantially complete. With the proportions given, the solution of mercaptide also contains a small amount of amyl mercaptan. w i

The aqueous soluti of sodium sulfona'te, as prepared above, is'heate to boiling and then the yellow anthraquinone thioethers aqueous mercaptide solution i s gradually A 1 I as while continuing the boiling; about one hour being required to so mix the amounts of the two aqueous solutions given ante. After all the mercaptide solution is added, the mixture is further boiled under reflux for a period of live hours or more until the reaction is complete and substantially all the alpha anthraquinone amyl thioether has precipitated.

The mixture is then cooled and permitted to Melting point F 011 at ordinary temperatures Sulfur, per cent 10.33 Color Golden-yellow Amyl thioether of alpha anthraquinone as prepared above may be represented by the following structural formula:

What we claim is:- 1. In the manufacture or organic thioethers of anthraquinone from alpha-anthraquinone sulionic acid, the improvement which comprises heating an aqueous solution of an alkali metal salt the organic thioether of alpha-anthraquinone so obtained.

2. In the manufacture of organic thioethers oi anthraquinone from alpha-anthraquinone, the improvement which comprises preparing an aqueous solution of an alkali metal salt of alphaanthraquinone sulfonic acid by dissolving said alkali metal salt in boiling water, separately preparing an aqueous solution of an alkali metal mercaptide by adding the mercaptan to an aqueous solution of caustic soda and stirring the mixture at room temperature until the formation of the, mercaptide is substantially complete, then gradually adding the said solution of alkali metal mercaptide to the said boiling solution of alkali metal salt or alpha-anthraquinone sulionic acid and further boiling the reaction mixture until the reaction is substantially complete and subsequently recovering the organic thioethers of alpha-anthraquinone from said reaction mixture.

3. The process of claim 2 wherein said sulfonate is sodium suli'onate.

4. The process of claim 2 wherein said mercaptide is sodium ethyl mercaptide.

5. The process of claim 2 wherein said mercaptide is sodium amyl mercaptide.

TROY LEE CANTREIL. JAMES o'mo TURNER. 

